Insights into cochlear structure by innovative light sheet fluorescence microscopy

Introduction About 0.5 billion people worldwide are currently suffering from disabling hearing loss. The causes are diverse, but many originate in the structures of the inner ear. Recent improvements in light sheet fluorescence microscopy allow nanometric examination of the whole intact cochlea in immunohistochemistry. These findings may contribute to identifying and quantifying disease mechanisms on a new scale and aid in the evaluation of novel gene therapies and their efficacy in the cochlea.

Methods Here, we evaluate the cochlear nano-structure using a cutting-edge, custom-built cleared tissue light sheet microscope (CTLSM), which provides an isotropic resolution of 0.8µm (pixel size 0.38µm). Native and genetically modified mouse cochleae were decalcified, stained, and cleared using an optimized iDisco+protocol. To quantify cochlear architecture, e.g., SGNs and hair cells, we establish a Stardist-based machine learning algorithm to detect cellular structures.

Results The high resolution of the CTLSM allows the assessment of SGN density along the Rosenthal's canal. For the first time, we can also map inner hair cells and their synapse distributions throughout the whole intact cochlea. Here, we generated robust immunostaining protocols to later elucidate SGN subtypes and correlate electrophysiological firing patterns. The CTLSM enables the study of distinct fluorescence patterns on a cellular to subcellular level to investigate hair cell synapses and validate transduction efficacies in gene therapies by colocalizing expression profiles.

Conclusion Structural analysis of cochlear architecture and its heterogeneity on a nanoscale level will contribute to the understanding of hearing, hearing restoration, and further the development of auditory prostheses.

Funding information DFG, EU and state funds

Publication History

Article published online:
19 April 2024